It has been determined that myopia (or nearsightedness) and astigmatism are directly related to the curvature of the eye, and in particular of the cornea. Varying the degree of curvature of the cornea will, therefore, directly affect the degree of myopia and astigmatism. Recently, surgical procedures have been developed to vary the degree of curvature of the cornea. These procedures involve the placement of radial incisions, varying in length, about the cornea and extending up to or into the sclera. Further descriptions of this surgical technique can be found in articles by Professor S. Fyodrov; William D. Myers, M.D.; Leo Bores, M.D.; Ronald A. Schacher, M.D., et al; Ronald A. Schacher, M.D. alone; and Ronald A. Schacher, M.D. with Les Schacher, M.D.; all published in the Proceedings of the Keratorefractive Society for the meeting dated June 21, 1980.
Heretofore, the placement of the radially arranged incisions has been accomplished by free hand. Placement and positioning of the incisions has thus far, been the result of the surgeons' eye judgment. The success or failure of the technique to vary the curvature of the cornea and hence correct the eyesight deficiency will depend on a variety of dimensional factors associated with the incisions (i.e. "slits").
It has been found that the depth of the incisions is a critical factor in determining the degree of varying the curvature of the cornea.
The length of the incisions, the remaining optical zone and the angle of the incisions with respect to the surface of the cornea are also critical factors in performing a successful procedure. It has been found desirable that the angle of the incisions be 90.degree. (i.e. perpendicular) with respect to the surface of the cornea. Perpendicular incisions will result in the thinnest possible scar width and thus minimal glare effect.
Incisions which are not perfectly radial will also have an effect on the results of such an operation.
Because control over the critical factors (i.e. spacing, length, depth and perpendicularity) are difficult, if not impossible to control when forming the incisions by free hand, the results to be expected from surgical procedures performed free hand cannot, therefore, be predicted. In addition, placement of corneal incisions by direct application of a knife blade to the surface of the cornea may cause excessive compression of the corneal wall thickness at the point of application and thus creates the danger of perforation.
It is, accordingly, a general object of the present invention to provide an ophthalmological surgical instrument, useful for forming radial incisions about the cornea which overcomes many of the disadvantages of using a free hand technique.
It is a more specific object of the present invention to provide a device to assist the surgeon in forming radial incisions in the cornea of the eye and which is capable of controlling the depth of the incision.
Another object of the invention is to provide a device of the foregoing type which is also capable of controlling the length of the radial incisions and therefore, the size of the optical zone.
Still a further object of this invention is to provide a device for assisting in the formation of radial incisions in the cornea which are perpendicular to the surface of the cornea.
Use of the present invention also minimizes the danger of perforating the cornea when forming such incisions by enlarging the area of contact to eliminate severe compression of the corneal wall.
The above objects, features and advantages, along with other objects, features and advantages of the present invention will become more apparent from the detailed description of the invention in conjunction with the accompanying drawings to be described more fully hereinafter.